The present invention relates to an open-sided bicycle tire and more specifically to a tire having a plurality of carcass plies and a breaker ply intermediate said plies under the tread.
A bicycle tire is likely to be broken or punctured if its tread is pierced with a nail or any other pointed object. A conventional tire is shown in FIG. 2. The tire 1' has a breaker 7' disposed between a tread 6' and carcass plies 2a' to 2c'. The breaker 7' comprises a fabric composed of one or more plies of synthetic fibers and having high tensile strength. The breaker generally provides high resiliency. Such a tire has a number of drawbacks, including the following:
1. The breaker 7' is subjected to a large strain due to the difference in elasticity of the breaker from the tread rubber 6' and the carcass plies 2a' to 2c' if the tire 1' is deformed on the road surface. A strain is also produced in the breaker 7', since the adhesive strength between the tread rubber 6' and the breaker 7' differs from the adhesive strength between the breaker 7' and the carcass plies 2a' to 2c'. Further, the elasticity between the breaker 7' and the tread rubber 6', and the elasticity between the tread rubber 6' and the carcass plies 2a' to 2c' are different from each other, so that the breaker 7' is subjected to high strain. The breaker 7', eventually fails to withstand those repeated strains due to external force, and is damaged by fatigue sooner than the other parts of the tire. Of course, the fatigue, breakage is promoted if the difference in elasticity between the breaker and the carcass is large. This results in the separation of the breaker from the tread rubber due to a reduction in adhesive strength. The tread rubber 6' is subjected to the repeated strain which acts thereon not only radially, but also axially. This results in not only the separation between the tread rubber and the breaker, but also the separation between the tread rubber and the carcass plies in areas beyond the edges of the breaker, leading finally to the entire separation of the tread rubber which renders the tire totally unusable.
2. The earlier damage of the breaker 7' reduces its cutting resistance, and reduces the cutting resistance of the tire.
3. In an open-sided tire, it is impossible to employ a breaker width which is greater than the tread width, and it has been usual to limit it to a maximum of 0.9 times as large as the tread width. Therefore, the shoulders of the tire do not have any means for improving their cutting resistance.